Heat the oven to 350°F. Line two large rimmed baking sheets with parchment paper or silicone baking mats.

In a medium bowl, whisk together the flour, baking soda, and fine salt.

In a stand mixer, beat the softened butter with the brown sugar and granulated sugar for 3 to 4 minutes until pale and fluffy.

Beat in the vanilla first, then add the eggs one at a time, scraping down the bowl after each addition.

Add the flour mixture on low speed in stages, mixing until no dry streaks remain. Fold in the chopped Butterfinger bars, keeping the pieces large.

Scoop level 2-tablespoon portions onto the prepared sheets, leaving space between each one.

Bake for about 10 minutes per tray, until the edges are golden and the centers still look slightly soft.

Let the cookies rest on the baking sheet for 5 minutes, then move them to a rack to cool.